Using genetic algorithm for the optimization of seismic behavior of steel planar frames with semi‐rigid connections

Beam‐column connections have a significant role in the results of the analysis and the design of steel frames. In this paper, a genetic algorithm has been used for the non‐linear analysis and design of steel frames. For minimizing the weight of frames, while satisfying the applied constraints and restraints such as the limits of normal and combined stresses, criteria such as target displacement(s) and the number and locations of plastic hinges were used. To analyze and design the frame elements, I and box‐shaped standard sections were used for beams and columns, respectively. Finally, some clues for finding optimizing semi‐rigid connection stiffness values for beam‐to‐column connections have been obtained. The degrees of these rigidities are obtained by a genetic algorithm during the procedure of optimization in order to reach a frame with the minimum weight. SAP2000 structural analysis program was used to perform modal analysis and linear and non‐linear static solutions as well as the design of the elements. A MATLAB program was written for the process of optimization. The procedure of optimization was based on a weight minimization carried out for 9 steel frames. Thus, the optimum connection stiffness could be obtained for minimizing the weight of the structure. The results show that the non‐linear analysis gives less weight for short period frames with semi‐rigid connections compared to those of linear ones. However, by increasing the periods of frames, much less weights are obtained in the case of non‐linear analysis with semi‐rigid connections.